What is the relative atomic mass (A_(r)) of COPPER? {}^63Cu:70% {}^65Cu:30% ((70+63)times (30+65))/(100)=126.35 ((70times 30)+(63times 65))/(100)=61.95 ((70times 63)+(30+65))/(100)=128 ((70times 63)+(30times 65))/(100)=63.6

## Step 1: Relationship UnderstandingIn this problem, we need to find the relative atomic mass of copper ( ) when two isotopes and are 70% and 30% abundant respectively. We recognise that relative atomic mass is calculated as the sum of the product of each isotope's abundance in decimal form and its respective mass.## Step 2: Isotope - Cu-63 CalculationThe relative abundance of Cu-63 is given in percentage form (70%). We convert it into decimal form by dividing it by 100. This gives (i.e., ).Then, we multiply it by the corresponding atomic mass number which is 63.This leads us to .## Step 3: Isotope - Cu-65 CalculationNow we repeat the process for Cu-65. Its relative abundance given is 30%. We convert this to decimal form by dividing that by 100 which is hence ( ).Then, we mulitply it by the atomic mass which leads to .## Step 4: Total Relative Atomic MassFinally, we need to add the weighted atomic mass of both isotopes according to their contributions to the atomic mass of copper. It will be the sum of the products obtained in step 2 and step 3. Therefore, by adding 44.1 and 19.5 we have . This is the relative atomic mass of copper.